1. Field of the Invention
The present invention relates to a recording-medium feeding device for an image forming apparatus, such as a photocopier, a printer, or a facsimile, to facilitate feeding a recording medium.
2. Description of the Related Art
Conventionally, a paper feeding device that feeds paper to an image forming unit or a printing unit from a bundle of paper loaded in a paper loading unit by separating the paper sheet by sheet by blowing air to the paper from an air outlet has been known for an image forming apparatus, such as a photocopier, and a printer. Particularly, a configuration that a nozzle opening is arranged on a part of a side fence below a passage of paper fed from a paper tray, and a pair of such nozzle openings are symmetrically arranged on a pair of side fences that are arranged opposingly to each other is known (see, for example, Japanese Patent Application Laid-open No. 2007-008656).
Another paper feeding device that includes a guide to restrict floating of paper when separating and feeding paper by blowing air is known (see, for example, Japanese Patent Application Laid-open No. 2006-321629).
As shown in FIG. 21A, Japanese Patent Application Laid-open No. 2007-008656 discloses a paper feeding device that includes an air outlet 601 that blows air, a paper feeding roller 603 that fees paper, and a paper-feeding plane P. The air outlet 601 is arranged vertically below the paper-feeding plane P. The air outlet 601 is configured to blow air from a lateral side of a paper feeding direction indicated by an arrow D when feeding paper, and to separate a top sheet of paper from the following sheet. However, according to Japanese Patent Application Laid-open No. 2007-008656, a vertical height of the air outlet 601 is insufficient, consequently, paper cannot be kept floating.
Japanese Patent Application Laid-open No. 2006-321629 discloses another paper feeding device that includes the air outlet 601, the paper feeding roller 603, and the paper-feeding plane P as shown in FIG. 21B. The air outlet 601 further includes an upper end guide 605. The air outlet 601 is formed to straddle the paper-feeding plane P vertically. However, despite that the air outlet 601 includes the upper end guide 605, a top sheet of paper tends to float too high. For this reason, according to Japanese Patent Application Laid-open No. 2006-321629, the paper cannot be fed with an appropriate angle to the paper feeding roller 603.
Paper feeding devices are often configured to use paper other than plain paper, such as coated paper, art paper, films, and the like, because of recent diversification of variations of paper. Particularly when using paper other than plain paper, the conventional paper feeding devices cannot feed paper appropriately to an image forming unit due to two problems described above. Consequently, there is a possibility that faulty paper feeding by the paper feeding device gives an adverse effect on forming image.
According to the above paper feeding devices, no inventive idea about a shape of the air outlet is described, and the shape of the air outlet is not taken into account.
To feed paper at an appropriate angle means to keep an angle of a sheet of paper to be appropriate to a paper feeding roller or a reverse roller of the paper tray in the description herein. The paper-feeding plane P means a plane P in the horizontal direction in contact with the bottom of the paper feeding roller 603.